I've generally heard the term used to refer to low-effort games that are basically just third-party assets packaged up and sold as a full experience, while having little to no "playable content". The availability of these assets could encourage this since they are freely available.

An "Asset Flip" is a commercial game puzzled together from ready-made bits as cheap as possible (e.g. get some shooter template code, drop in some free/cheap character and weapon models, copy or make some really basic levels), without consideration for the quality of the resulting game.

If you've ever followed a Hello World game building tutorial for UE or Unity, somebody has taken the end result of that tutorial and placed it on a game marketplace somewhere.

It was/is a bit taboo, but the gaming phenomena PUBG also used UE marketplace assets, although they added value by making an enjoyable game around it.